1. Field of the Invention
This invention relates to an improved collar seal for plastic lined pipe and a method of using the same. More specifically, this invention relates to a plastic collar seal for downhole use in oil field applications for protecting the plastic lined pipe at the pipe joint.
2. Description of the Prior Art
The concept of employing a plastic lined pipe in an oil or gas well which is to be treated with highly corrosive fluid is a known and accepted commercial practice. Thus, it is known to use a pvc lined steel pipe to deliver acids and the like to a desired depth in a gas or oil well. It is also well known that such pipes or tubing involve the assembling of many shorter pipe sections wherein each pipe joint created at the junction of two pipe sections represents a potential weak point and region susceptible to acid or corrosive attack. Thus, to extend the life of the plastic lined pipe, various gaskets or pipeline couplings have been proposed with varying degrees of success, yet none have proven to be entirely reliable. For example, the use of an internal gasket to be held under compression between the two respective pipe ends seems to be a reasonable solution. However, in practice, the repeated assembling and disassembling of pipe under oil field conditions quickly leads to a high frequency of pipe joint failure for compressive gasket type pipe couplings. Thus, the need for a reliable yet easily installed and reuseable plastic lined pipe joint, particularly for oil field applications, still exists.